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Review: 3 Phases of Matter

Solid

Liquid

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What is a Phase Change?

It is a change from one state of matter

(solid, liquid, gas) to another.

Phase changes are physical changes because:

- It only affects physical appearance, not

chemical make-up.

- Reversible

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What happens during a phase change?

During a phase change, heat energy is either absorbed or released.

Exothermic - Heat energy is released as molecules slow down and move closer together.

Endothermic - Heat energy is absorbed as molecules speed up and expand.

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Melting

Phase change from a solid to a liquid

Molecules speed up, move farther apart, and absorb heat energy

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Freezing

Phase Change from a liquid to a solid

Molecule slow down, move closer together and release heat energy.

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Vaporization (Boiling)

Phase change from a liquid to gas. It occurs at the boiling point of matter.

Molecules speed up, move farther apart, and absorb heat energy.

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Evaporation

Phase change from a liquid to a gas on the surface of a liquid (occurs at all temperatures).

Molecules speed up, move farther apart, and absorb heat energy.

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Condensation

Phase change from a gas to a liquid.

Molecule slow down, move closer together and release heat energy.

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Sublimation

Phase change from a solid to a gas.

Molecules speed up, move farther apart, and absorb heat energy.

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Deposition

Phase change from a gas to a solid.

Molecules slow down, move closer together and release heat energy.

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Types of Phase Changes

Types of Phase Changes

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A question to ponder…

Does the temperature of a substance change as the a state change is occurring?
Things to keep in mind

Water freezes/melts and 0 degrees Celsius
Water boils/condenses at 100 degrees Celsius
Time can also mean energy added or removed

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Heat (thermal energy)

Temperature º C.

100

solid

liquid

gas

Water Phase Change Graph

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Change of State vs. Change in Temperature

When a substance gains or loses energy it must either change temperature or change state but NEVER both.

During state change the added energy causes particles to spread out and go through a phase change

During temperature change the energy is really just making particles move faster

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Graphing a Phase Change

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Heat (thermal energy)

Temperature º C.

100

melting

freezing

condensing

boiling

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Melting & Boiling Points

Melting Point: The temperature at which a solid changes into a liquid.

Boiling Point: The temperature at which a liquid changes into a gas.

What is a Freezing point? Compare the freezing and melting points of water.

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